Hepatocyte nuclear factor 4 provokes expression of epithelial marker genes, acting as a morphogen in dedifferentiated hepatoma cells.
We have recently shown that stable expression of an epitope-tagged cDNA of the hepatocyte- enriched transcription factor, hepatocyte nuclear factor (HNF)4, in dedifferentiated rat hepatoma H5 cells is sufficient to provoke reexpression of a set of hepatocyte marker genes. Here, we demonstrate that the effects of HNF4 expression extend to the reestablishment of differentiated epithelial cell morphology and simple epithelial polarity. The acquisition of epithelial morphology occurs in two steps. First, expression of HNF4 results in reexpression of cytokeratin proteins and partial reestablishment of E-cadherin production. Only the transfectants are competent to respond to the synthetic glucocorticoid dexamethasone, which induces the second step of morphogenesis, including formation of the junctional complex and expression of a polarized cell phenotype. Cell fusion experiments revealed that the transfectant cells, which show only partial restoration of E-cadherin expression, produce an extinguisher that is capable of acting in trans to downregulate the E-cadherin gene of well-differentiated hepatoma cells. Bypass of this repression by stable expression of E-cadherin in H5 cells is sufficient to establish some epithelial cell characteristics, implying that the morphogenic potential of HNF4 in hepatic cells acts via activation of the E-cadherin gene. Thus, HNF4 seems to integrate the genetic programs of liver-specific gene expression and epithelial morphogenesis.
Späth
G F
GF
Unité de Génétique de la Différenciation, URA 1149, Centre National de la Recherche Scientifique, Département de Biologie Moléculaire, Institut Pasteur, 75724 Paris, France.
Weiss
M C
MC
D000287:Administration, Topical; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D014408:Biomarkers, Tumor / Q000235:genetics; D015820:Cadherins / Q000235:genetics / Q000502:physiology; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D002448:Cell Adhesion / Q000235:genetics / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D002455:Cell Division / Q000187:drug effects; D016764:Cell Polarity / Q000187:drug effects; D004268:DNA-Binding Proteins; D003907:Dexamethasone / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression / Q000235:genetics / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D052138:Genes, Neoplasm / Q000235:genetics*; D005938:Glucocorticoids / Q000494:pharmacology; D006133:Growth Substances / Q000502:physiology*; D051557:Hepatocyte Nuclear Factor 4; D006822:Hybrid Cells / Q000378:metabolism; D010750:Phosphoproteins / Q000502:physiology*; D051381:Rats; D014157:Transcription Factors / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured
D000893:Anti-Inflammatory Agents; D014408:Biomarkers, Tumor; D015820:Cadherins; D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D006133:Growth Substances; D051557:Hepatocyte Nuclear Factor 4; D010750:Phosphoproteins; D014157:Transcription Factors; D003907:Dexamethasone